Although refractive error is the most common of all eye anomalies, little is understood about its effect on pathway coding and the transmission of information to the visual cortex and other processing centers. The purpose of this study is to quantitatively describe, on a single cell basis, the alterations in pathway activity resulting from defined alterations of the visual stimulus, both by induced refractive error (in conjunction with a mathematical analog developed to predict the quality of the retinal image) and by an external blur model technique which allows a direct detailed photometric analysis of the stimulus. The pathway responses corresponding to these two types of stimulus degradation methods and recorded from each major level (e.g. retinal ganglion cell, lateral geniculate nucleus, superior colliculus, Vision I of the cortex) will then be analyzed for equivalence, and the retained fidelity of particular types of information (e.g. movement detection, contrast sensitivity, intermodality gating thresholds, directional selectivity) as they progress from level to level will be quantitatively evaluated. A comprehensive quantitative description of refractive error effects on all major levels, from retina to cortex, will first be completed for the rabbit, following up the exploratory pilot experiments already published. Once the techniques for such analyses have been fully refined for this visual system, with its well-defined peripheral mechanisms (e.g. retinal directional selectivity), then the pure core systems and the mixed rod-cone systems of the advanced primates can be most effectively and economically evaluated. BIBLIOGRAPHIC REFERENCES: Ritchie, G.D., Lee, A.A., Gast, T.J. and Hill, R.M., Is There a Single Cell Code for Background Light Levels? Experientia 31:656, 1975. Hill, R.M., Ritchie, G.D., Bohman, C.E., S.A., and Hughes, H.C., Retinal Blur and Midbrain Cell Response. Experientia (in press) 1976.